DESCRIPTION: This application proposes continuing a study for years 6-10. The investigators are studying the effect of rigid and non-rigid attachment of natural teeth to osseointegrated implants. The previous applications recommended recruiting fifty patients who were missing all the maxillary teeth and mandibular right and left second premolars and molars for the study. Each patient received a one two-staged hydroxyapatite-coated implant on each side of the mandible in the first molar area. A bridge was attached to the first mandibular premolar and the hydroxyapatite implant. On one side, the bridge was attached to the premolar and implant using a rigid technique while on the opposite side, the bridge was attached using a non-rigid, semi- precision slot attachment. A maxillary denture opposed the bridges. The patients are examined every 6 months. Standardized radiographs, soft tissue exams, and satisfaction evaluations are performed every six months. The investigators had planned to recruit 20 patients in each of the first 2 years and 10 patients in the third year. However, their recruitment process has taken longer than planned. A total of 42 patients was recruited during the first 4 years of the study. Most of the patients were recruited and restored in years 3 and 4 rather than in years 1 and 2. The investigators have not changed the study protocol from the previously approved grant. They are requesting funding to support 5 more years of follow-up on the 42 patients. They do not plan to recruit any new patients. The effects of the bridge attachment between osseointegrated implants and natural teeth will be evaluated using measurements of gingival bleeding, plaque and calculus indices, presence of attached gingiva, vertical bone loss using standard radiographs, and tooth and implant mobility.